Air conditioning system including humidity control sensing means



Oct. 10, 1967 v O N 3,346,040

AIR CONDITIONING SYSTEM INCLUDING HUMIDITY'CONTROL SENSING MEANS Filed Sept. 7, 1965 2 Sheets-Sheet 1 33 INVENTOR.

meapalee' Oct. 10, 1967 "r. COHEN 3,346,040

- AIR CONDITIONING SYSTEM INCLUDING HUMIDITY CONTROL SENSING MEANS Filed Sept. 7, 1965 2 Sheets-Sheet INVENTOR I THEODO RE C OHE/l/ ATTORNEY 3,346,040 AIR C(PNDITIONING SYSTEM INCLUDING HU- MIDITY CONTROL SENSING MEANS Theodore Cohen, 55 Ruxton Road,

Great Neck, NY. 11023 Filed Sept. 7, 1965, Ser. No. 485,325 2 Claims. (Cl. 165--21) This invention relates to the art of air conditioning systems, more particularly of the fresh air intake type.

As conducive to an understanding of the invention, it is noted that in many applications using air conditioning systems, it is essential that the outside or ambient air be drawn into the system and cooled for circulation into the room or other area to be cooled and the cooled air discharge to the outside after it has passed through the room to be cooled.

This is especially true in some places as operating rooms in hospitals where gases used during operations must be eliminated and hence there must be a constant fresh air intake and cooled air discharge to the outside. There are, of course, many other applications such as in industrial plants where fresh air intake is essential.

However, numerous problems exist when fresh air must constantly be cooled.

Thus, it is to be noted that the dry bulb temperature and the relative humidity of the fresh air entering an air conditioning system varies over a wide range during the course of a summer season and even during the course of any one day.

Some systems, especially in the eastern region of the United States, are designated for fresh air entering the system at 95 F. dry bulb and 75 F. wet bulb which is equivalent to 95 F. wet bulb and 40% relative humidity. However, the range of conditions that actually occurs varies widely from this optimum and in different situations the following typical measurements have been made by the United States -Weather Bureau:

Dry Ibulb temperature: Relative humidity, percent Generally speaking, the cooling coils of the most efficient air conditioning units can only. provide a 90% relative humidity, that is, the air immediately after it leaves the coils is at 90% relative humidity and say 58 F. dry bulb temperature. Where it is desired to have the room area at say 75 F. and 50% relative humidity, it is apparent that the air as it is discharged from the cooling coils must warm up from such lower temperature of say, 58 F. dry bulb.

Consequently, where the original humidity of the fresh air is high and the temperature is relatively low, the temperature of the air in the room to be cooled cannot be brought down to the desired value while at the same time bringing the humidity down to a comfortable level.

It is accordingly among the objects of the invention to provide an air conditioning system of substantially conventional type which is designed to continually draw fresh air into the system and which incorporates control mechanism that may readily be installed with minormodifications in the standard equipment and which will permit the temperature and humidity in the room to be conditioned, to be within predetermined and desired limits regardless of the temperature and relative humidity of the fresh air brought into the system.

According to the invention, these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claims.

United States Patent 3,346,040 Patented Oct. 10, 1967.

In the accompanying drawings in which is shown one of various possible embodiment of the several features of the invention,

FIG. 1 is a diagrammatic view of an air conditioning system,

FIG. 2 is a diagrammatic view illustrating the connection of the control devices of the present invention, and

FIG. 3 is a chart illustrating in broken lines the operation of a conventional air conditioning system, and in solid lines the operation of the air conditioning system according to the present invention.

Referring now to the drawings, as shown in FIG. 1, the air conditioning system includes an air conditioning unit 11 of substanitally conventional type having a fresh 'air intake 12 connected by suitable conduits (not shown) to a source of fresh air.

The fresh air entering the intake 12 is drawn through a chamber 13 and then passes through the preheating coils 14, a dust filter 15 and cooling coils 16.

The cooled air is then drawn through a blower 17 to be discharged through supply ducts (not shown) from the outlet 18 of the blower 17.

The cooling coils 16 are cooled in a conventional manner by means of suitable refrigeration equipment 19 in conjunction with the ancillary equipment such as a water cooling tower 21, water pumps 22 and 23 and the like.

As the cooling coils may be cooled in any suitable manner and the particular means for cooling such coils is not per se part of the invention, it will not be described further.

The preheat coils also may be of any suitable type and in the illustrative embodiment, they may be heated by a source of steam, or hot water connected to valve 24.

According to the invention, as shown diagrammatically, in FIGS. 1 and 2, a humidity sensing device 31 is positioned in the fresh air intake between the intake 12 and the preheat coils 14. Although any humidity sensing device may be utilized, in the embodiment herein shown, a pneumatic humidistat of the type put out by the Honeywell Corporation under Model No. HP-900 and identified :by its trademark HUMID-U-STAT is preferred.

In addition, there is positioned between the preheat coils 14 and the filter 15, a temperature sensing device 32 which senses the dry bulb temperature of the air after it passes the preheat coils 14.

The temperature sensing device also is of conventional type such as that put out by the Honeywell Corporation under Model No. T-915 ND.

As is shown in FIG. 2, the humidity sensing device 31 is energized by a source of compressed air fed to inlet 33 of the device. Based on the humidity of the air entering the fresh air intake 12, which is determined by the sensing element 34, the output pressure from port 35 of the device 31 will be determined and this output will be applied to control port 36 of the temperature sensing device 32.

The temperature sensing device 32 is also supplied with compressed air to port 37 and the outlet port 38 of the temperature sensing device 32 will apply air pressure to control valve 24 based on the dry bulb temperature measured by the sensing element 39 as well as the humidity determined by the sensing element 34.

Thus, the control valve 24 will be actuated an amount which is related to the relative humidity of the air entering the fresh air intake and the temperature of the air after it passes the preheat coils 14.

As a result of the setting of the control valve 24, the steam supply, for example, to the preheat coils 14 will be varied to increase or decrease the temperature of the preheat coils 14.

In the operation of the air conditioning system, it is turned on in conventional manner and the fresh air will be drawn through the intake 12 and pass through the cooling coils 16 so that the air is cooled for discharge by the blower 17 into the chambers to be cooled.

In conventional air conditioning systems which, for example, are designed to operate with freh air entering the system at a maximum of 95 F. dry bulb and 40% relative humidity, if in fact the air enters the system at 69 F. dry bulb and 85% relative humidity, referring to the chart, FIG. 3, where A indicates the condition of the air entering the system, if the room to be cooled is to be maintained at a temperature of 75 F. dry bulb and a humidity of 50%, the conventional system will not achieve such results.

Thus, the design of all cooling coil is such that referring to the chart FIG. 3, the most effective conditioning process line that can be obtained is a line tangent to the saturation line (100% relative humidity). This is the most efficient process that any cooling coil can produce. Thus, such line will extend from A to B (tangent to the saturation line).

Since practically the most efficient air conditioners provide 90% relative humidity to the air as it leaves the cooling coils, the dry bulb temperature of such air in the line A-B will be at C and equals to 64 F. dry bulb.

Thus, the air supplied to the space to be cooled will have a humidity of 90% and a dry bulb temperature of 64 F. when it leaves the cooling coils 16.

The internal load of the air conditioned space, in the illustrative example herein, will heat the conditioned air 17 F., so that the room temperature will be at point D, i.e., 81 F. dry bulb and 52% relative humidity.

Thus, the temperature and humidity would be in excess of that required for comfort, i.e., 75 F. dry bulb and 50% relative humidity.

According to the invention, herein, the air entering the system will be at point A on the chart FIG. 3, i.e., it will have a dry bulb temperature of 69 F. and 85% relative humidity.

The humidity sensing device 31 in the fresh air intake will sense the humidity of the entering air and since the humidity is above the amount desired to which the device is set, a control signal will flow to the control port 36 of the temperature sensing device 32 and provide an output signal from port 38 to the control valve 24 which regulates the flow of steam to the preheat coils 14 so that such coils will heat the fresh air to a temperature of say 85 F. dry bulb, say at point B on the chart, FIG. 3, at which temperature the humidity will be 50%.

The preheated air will then pass through the cooling coils 16 and will be cooled to say 58 F. dry bulb and 90% relative humidity. This is indicated by the line EF which is a practical process line available with modern air conditioning equipment.

For the same internal load conditions as above set forth, i.e., a temperature rise of 17 F. in the room to be cooled, the process line will extend from point F to point G. The resultant space conditions at point G will thus be 75 F. and 50% relative humidity as desired.

As above described, the relative humidity control 31 acts as a master control to reset the control point of the temperature sensing device 32. As the relative humidity of the ambient air increases, the control point of the temperature sensing device 32 is raised and as the relative humidity of the ambient air drops, the control point of the temperature sensing device is lowered.

For example, at 40% relative humidity, the set point of the temperature sensing device 32 would be 60 F. and at 90% relative humidity the set point of the temperature sensing device would be 85 F.

Although, as herein described, the unit is pneumatically controlled, it is apparent that it can be electronically or electrically controlled.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description, or shown in the accompanying drawing, shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. An air conditioning system of the fresh air intake type comprising a fresh air intake, a blower to draw air through said intake and discharge the same after it has been conditioned, cooling means between the intake and the blower, heating means between the intake and the cooling means, sensing means to vary the temperature of the air passing the heating unit before flow of such air through the cooling means, said sensing means comprising a humidity sensing device, an adjustable temperature sensing device having an adjustable control point, said temperature sensing device being positioned between said heating means and said cooling means, said humidity sensing device being controlled by variations in the relative humidity of the air entering the air intake, said humidity sensing device and said temperature sensing device being of the pneumatic type each having an air pressure inlet to provide a control pressure, said humidity sensing device having a pressure outlet, said temperature sensing device having a control pressure inlet connected to said pressure outlet and also having a control pressure outlet controlling the temperature of said heating means, whereby variations in the humidity sensed by said humidity sensing device will cause corresponding pressure variations applied to the pressure inlet of the temperature sensing device to change the control point of said temperature sensing device for corresponding variations in the control pressure outlet to correspondingly change the temperature of the heating means.

2. The combination set forth in claim 1 in which said heating means comprise-s a coil through which a heated fluid may flow, a valve controlling flow of such heated fluid through said coil, said control pressure outlet of said temperature control device being connected to said valve to control the latter.

References Cited UNITED STATES PATENTS 1,819,643 8/1931 Fleisher l-21 X 1,827,099 10/1931 Otis l652l 2,053,042 9/1936 Otto l6521 2,106,083 l/1938 Chappell et al 23644 2,l77,49.6 10/1939 Miller et al l65-l6 2,204,016 6/1940 Karlson 23644 2,426,827 9/1947 Hemming et al. l6516 X 2,953,355 9/1960 Hungate 23644 X ROBERT A. O?LEARY, Primary Examiner.

MEYER PERLIN, Examiner.

M- A. ANT NAK S, s nt x m r, 

1. AN AIR CONDITIONING SYSTEM OF THE FRESH AIR INTAKE TYPE COMPRISING A FRESH AIR INTAKE, A BLOWER TO DRAW AIR THROUGH SAID INTAKE AND DISCHARGE THE SAME AFTER IT HAS BEEN CONDITIONED, COOLING MEANS BETWEEN THE INTAKE AND THE BLOWER, HEATING MEANS BETWEEN THE INTAKE AND THE COOLING MEANS, SENSING MEANS TO VARY THE TEMPERATURE OF THE AIR PASSING THE HEATING UNIT BEFORE FLOW OF SUCH AIR THROUGH THE COOLING MEANS, SAID SENSING MEANS COMPRISING A HUMIDITY SENSING DEVICE, AN ADJUSTABLE TEMPERATURE SENSING DEVICE HAVING AN ADJUSTABLE CONTROL POINT SAID TEMPERATURE SENSING DEVICE BEING POSITIONED BETWEEN SAID HEATING MEANS AND SAID COOLING MEANS, SAID HUMIDITY SENSING DEVICE BEING CONTROLLED BY VARIATIONS IN THE RELATIVE HUMIDITY OF THE AIR ENTERING THE AIR INTAKE, SAID HUMIDITY SENSING DEVICE AND SAID TEMPERATURE SENSING DEVICE BEING OF THE PNEUMATIC TYPE EACH HAVING AN AIR PRESSURE INLET TO PROVIDE A CONTROL PRESSURE, SAID HUMIDITY SENSING DEVICE HAVING A PRESSURE OUTLET, SAID TEMPERATURE SENSING DEVICE HAVING A CONTROL PRESSURE INLET CONNECTED TO SAID PRESSURE OUTLET AND ALSO HAVING A CONTROL PRESSURE OUTLET CONTROLLING THE TEMPERATURE OF SAID HEATING MEANS, WHEREBY VARIATIONS IN THE HUMIDITY SENSED BY SAID HUMIDITY SENSING DEVICE WILL CAUSE CORRESPONDING PRESSURE VARIATIONS APPLIED TO THE PRESSURE INLET OF THE TEMPERATURE SENSING DEVICE TO CHANGE THE CONTROL POINT OF SAID TEMPERATURE SENSING DEVICE FOR CORRESPONDING VARIATIONS IN THE CONTROL PRESSURE OUTLET TO CORRESPONDINGLY CHANGE THE TEMPERATURE OF THE HEATING MEANS. 